Definition of the derivative at a point x = a

Use the example from the definition of the derivative, f'(x)=2x. To find the derivative at a specific point x=a, plus in your a value into the derivative for x.

Ex: x=3
f'(x)=2x
f'(3)=2(3)
f'(3)=6 (the slope at the point x=a is 6)